1、Designation: D 2896 07aDesignation: 276/95An American National StandardStandard Test Method forBase Number of Petroleum Products by PotentiometricPerchloric Acid Titration1This standard is issued under the fixed designation D 2896; the number immediately following the designation indicates the year
2、oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Departmen
3、t of Defense.1. Scope*1.1 This test method covers the determination of basicconstituents in petroleum products by titration with perchloricacid in glacial acetic acid.1.2 Procedures A and B use different titration solventvolumes and sample weights.NOTE 1A round robin on a series of new and used oils
4、 and additiveconcentrates has shown that the two procedures give statistically equiva-lent results.1.3 Appendix X2 provides the use of an alternative solventsystem which eliminates the use of chlorobenzene in this testmethod. The use of the alternative solvent gives statisticallyequivalent results;
5、however, the precision is worse. ParagraphX2.5.5 provides guidance when comparing results using thetwo different solvents.1.4 The constituents that may be considered to have basiccharacteristics include organic and inorganic bases, aminocompounds, salts of weak acids (soaps), basic salts of polya-ci
6、dic bases, and salts of heavy metals.NOTE 2This test method is applicable to both fresh oils and used oilsas described in Sections 16, 17, and 19 and Appendix X1.1.5 This test method can be used to determine base number300 mg KOH/g. However, the precision statement in Section19 has been obtained onl
7、y on base number #300 mg KOH/g.1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of
8、this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificwarning statements, see Section 7, Section 10, and X2.2.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent Water3. Termino
9、logy3.1 Definitions of Terms Specific to This Standard:3.1.1 base numberthe quantity of perchloric acid ex-pressed in terms of the equivalent number of milligrams ofpotassium hydroxide that are required to titrate1gofthesample dissolved in the specified solvent to a well-definedinflection point as s
10、pecified in this test method.4. Summary of Test Method4.1 The sample is dissolved in an essentially anhydrousmixture of chlorobenzene and glacial acetic acid and titratedwith a solution of perchloric acid in glacial acetic acid usingpotentiometric titrimeter. A glass indicating electrode and arefere
11、nce electrode are used, the latter being connected withthe sample solution by means of a salt bridge. The meterreadings are plotted against the respective volumes of titratingsolution, and the end point is taken at the inflection in theresulting curve.4.2 ProcedureAuses 120 mL of titration solvent.
12、ProcedureB uses 60 mL of titration solvent. In addition, the twoprocedures use different equations for the calculation of appro-priate sample weights. Since many portions of the test methodare identical for Procedures A and B, only the unique sectionswill be described separately for the two versions
13、 of the testmethod.4.3 Occasionally certain used oils give no inflection in theforward titration mode, in which case a back titration modifi-cation with sodium acetate titrant is employed.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the
14、 direct responsibility of SubcommitteeD02.06 on Analysis of Lubricants.Current edition approved July 15, 2007. Published August 2007. Originallyapproved in 1970. Last previous edition approved in 2007 as D 289607.This test method has been approved by the sponsoring committees and acceptedby the coop
15、erating societies in accordance with established procedures.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1
16、*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 New and used petroleum products can contain basicconstituents that are present as additives.
17、The relative amountsof these materials can be determined by titration with acids.The base number is a measure of the amount of basic substancein the oil, always under the conditions of the test. It issometimes used as a measure of lubricant degradation inservice; however, any condemning limits must
18、be empiricallyestablished.6. Apparatus6.1 Potentiometric Titrimeters, either automatic recordingor manual.6.2 Glass Electrode, pH 0 to 11, general-purpose type.6.3 Reference Electrode, silver/silver chloride (Ag/AgCl)reference electrode with a nonaqueous bridge as described inSection 10. (See also 1
19、9.1.)NOTE 3Some reference electrodes with fritted or fiber diaphragmsand some combined glass plus reference electrodes systems are commer-cially available, such as the single-rod glass plus silver/silver chlorideelectrode assembly. During the development of this test method, the use ofelectrodes of
20、these types gave problems in some laboratories, but not inothers. Accordingly, these electrodes are permitted in this test method,provided that the sodium perchlorate bridge is used; however, whenstability or other problems arise with their use, the sleeve-type electrodeshould be used.6.4 Stirrer, e
21、ither mechanical or electrical, with variablespeeds and with propeller or paddle of chemically inertmaterial. When an electrical stirrer is used, it must be groundedso that disconnecting or connecting the power to the motor willnot produce a permanent change in meter reading during thecourse of a ti
22、tration. A magnetic stirrer with stirring bar can beused provided it meets these conditions.6.5 Buret, 10 or 20-mL, graduated in 0.05-mL divisions andcalibrated with an accuracy of 60.02 mL, or an automaticburet of similar accuracy.6.6 Titration Beaker, made of borosilicate glass or othersuitable ti
23、tration beaker, tall form recommended.6.6.1 For Procedure A, use a beaker of 250 or 300 mLcapacity. For Procedure B, use a beaker of about 150 mLcapacity such that 60 mL of titration solvent will cover theelectrodes.NOTE 4Other beakers of suitable size capacity may be used.6.7 Titration Stand, suita
24、ble to support the beaker, elec-trodes, stirrer, and buret. An arrangement that allows for theremoval of the beaker without disturbing the electrodes, buret,and stirrer is desirable.NOTE 5Some apparatus may be sensitive to interference by staticelectricity, shown by erratic movements of recorder pen
25、 or meter indicator,when the titration assembly (beaker and electrodes) is approached by theoperator. In this case surround the beaker closely with a cylinder of coppergauze that is electrically grounded.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests
26、. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsuffici
27、ently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water that meetsthe requirement of either Type I, II, or III of SpecificationD 1193.7.3 Acetic Acid, glacial (W
28、arningToxic and irritant).7.4 Acetic Anhydride (WarningToxic and irritant).7.5 Chlorobenzene (WarningToxic and irritant).7.6 Perchloric Acid, Standard Solution in AceticAcid (0.1 N)4(WarningPowerful oxidant when dry orheated. Great care should be taken to avoid contact withorganic matter under condi
29、tions that may result in subsequentdrying or heating, and spills should be washed immediatelyand thoroughly with water)Mix 8.5 mL of 70 to 72 %perchloric acid (HClO4,70to72%)(or10.2 mL of 60 to 62 %HClO4solution) with 500 mL of glacial acetic and 30 mL (or35 mL if the 60 to 62 % HClO4solution is use
30、d) of aceticanhydride. Dilute to 1 L with glacial acetic acid. Allow thesolution to stand for 24 h.NOTE 6Excess acetic anhydride should be avoided to prevent acety-lation of any primary or secondary amines that may be present.7.7 Potassium Hydrogen Phthalate(KHC8H4O4).7.8 Sodium Perchlorate Electrol
31、yte(WarningSodiumperchlorate is toxic and an irritant. It is also a powerfuloxidizing agent when heated. Great care should be taken toavoid contact with organic matter under conditions that mayresult in subsequent drying or heating, and spills should bewashed immediately and thoroughly with water.)
32、Prepare asaturated solution of sodium perchlorate (NaClO4) in glacialacetic acid. An excess of undissolved NaClO4shall always bepresent at the bottom of the solution.7.9 Titration SolventAdd one volume of glacial aceticacid to two volumes of chlorobenzene.7.10 Sodium Carbonate, anhydrous (Na2CO3).7.
33、11 Sodium Acetate Solution, 0.1 N in acetic acid (for backtitration, see Sections 16 and 17)Dissolve 5.3 g of anhydrousNa2CO3in 300 mL of glacial acetic acid. Dilute to 1 L withacetic acid after solution is complete.8. Standardization of Reagents8.1 Perchloric Acid SolutionThe standardization of the
34、perchloric acid solution (HClO4) differs for the two proceduresas follows:8.1.1 Procedure A (120 mL)Heat a quantity of potassiumhydrogen phthalate in an oven at 120C for 2 h and allow it tocool. Take 0.1 to 0.2 g of the potassium hydrogen phthalateweighed to the nearest 0.1 mg and dissolve it in 40
35、mLof warm3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States
36、Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4Available commercially for purchase already prepared.D 2896 07a2glacial acetic acid. Add 80 mL of chlorobenzene, cool, andtitrate with 0.1 N HClO4solution, using the electrode systemand procedures given in
37、10.1 to 10.4 and 11.4 to 11.7. Detectthe end point by the same procedure used for base numberdetermination (see 14.2). Carry out a blank titration on 40 mLof glacial acetic acid plus 80 mL of chlorobenzene (see 11.8).8.1.2 Procedure B (60 mL)Heat a quantity of potassiumhydrogen phthalate in an oven
38、at 120C for 2 h and allow it tocool. Take 0.05 to 0.1 g of the potassium hydrogen phthalateweighed to the nearest 0.1 mg and dissolve it in 20 mLof warmglacial acetic acid. Add 40 mL of chlorobenzene, cool, andtitrate with 0.1 N HClO4solution as described in 8.1.1. Carryout a blank titration on 20 m
39、L of glacial acetic acid and 40 mLof chlorobenzene (see 11.8).8.1.3 Calculate the normality, NA, of the HClO4solution asfollows:NA5 1000W/204.23V b!# (1)where:W = potassium hydrogen phthalate, g,V = HClO4solution used, mL, andb = volume corresponding to V for the blank titration,mL.NOTE 7Because of
40、the relatively large coefficient of volumetricexpansion of organic liquids, the acetous HClO4solution should be usedwithin 6 5C of the temperature at which it was standardized. If used ata temperature more than 5C higher, multiply the volume used by thefactor 1 (t0.001). If used at a temperature mor
41、e than 5C lower,multiply by the factor 1 + (t0.001), where tis the difference in degreesCelsius between temperatures of standardization and use and is alwayspositive.8.2 Sodium Acetate SolutionThe standardization of thesodium acetate solution (Na2CO3) differs for the two proce-dures as follows:8.2.1
42、 Procedure A (120 mL)Use 120 mL of titrationsolvent and 8.00 mLof 0.1 NHClO4solution.Titrate with 0.1 Nsodium acetate solution, using the electrode system and pro-cedure given in 10.1 to 10.4 and 11.4 to 11.7. Detect the endpoint by the same procedure as will be used for base numberdetermination (se
43、e 14.2). Calculate the normality, NB,ofthesodium acetate solution as follows:NB5 8.00 b!NA#/G (2)where:b = volume corresponding to V for the blank titration,NA= normality of the HClO4solution, andG = volume of standard sodium acetate used in thestandardization, mL.8.2.2 Procedure B (60 mL)Use 60 mL
44、of titration solventand 4.00 mL of 0.1 N HClO4solution. Titrate as described in8.2.1. Calculate the normality, NB, of the sodium acetatesolution as follows:NB5 4.00 b!NA#/G (3)where:b = volume corresponding to V for the blank titration,NA= normality of the HClO4solution, andG = volume of standard ac
45、etous sodium acetate used inthe standardization, mL.9. Preparation of Sample9.1 It is essential to ensure that the sample is representativesince any sediment can be acidic or basic or have adsorbedacidic or basic material from the sample. When necessary,samples are warmed to aid mixing. Used oils sh
46、ould bevigorously shaken to ensure homogeneity before sampling.NOTE 8As used oils can change appreciably in storage, samplesshould be tested as soon as possible after removal from the lubricatingsystem and the dates of sampling and testing, if known, should be noted.10. Preparation of Electrode Syst
47、em10.1 Preparation of ElectrodesWhen the reference elec-trode is to be changed from aqueous bridge to nonaqueous,drain out the aqueous solution, wash out all crystals of KClwith water, then rinse the outer jacket (salt bridge) severaltimes with NaClO4electrolyte solution. Finally fill the outerjacke
48、t with NaClO4electrolyte solution up to the filling hole.When using the sleeve-type electrode, carefully remove theground-glass sleeve and thoroughly wipe both ground surfaces.Replace the sleeve loosely and allow a few drops of electrolyteto drain through to flush the ground-glass joint and to wet t
49、heground surfaces thoroughly with electrolyte. Set the sleevefirmly in place, refill the outer jacket with the NaClO4electrolyte solution, and rinse the electrode with chloroben-zene. When in use, the electrolyte level in the referenceelectrode should be kept above that of the liquid in the titrationbeaker to prevent entry of contaminants into the salt bridge.When not in use, fill the reference electrode with the NaClO4electrolyte solution, leave the bung in the filling orifice, andimmerse both electrodes in distilled water, keeping the
